diff --git a/clap_mangen/tests/snapshots/flatten_arg_required.roff b/clap_mangen/tests/snapshots/flatten_arg_required.roff
new file mode 100644
index 00000000000..4e3016bba1c
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_arg_required.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR <\fB\-\-parent\fR> [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR <\fB\-\-child\fR> [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR <\fB\-\-child\fR> [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_basic.roff b/clap_mangen/tests/snapshots/flatten_basic.roff
new file mode 100644
index 00000000000..be64adbdd50
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_basic.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_help_cmd.roff b/clap_mangen/tests/snapshots/flatten_help_cmd.roff
new file mode 100644
index 00000000000..23028212879
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_help_cmd.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+bar
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help (see a summary with \*(Aq\-h\*(Aq)
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+long some
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_hidden_command.roff b/clap_mangen/tests/snapshots/flatten_hidden_command.roff
new file mode 100644
index 00000000000..21ef1ab791f
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_hidden_command.roff
@@ -0,0 +1,34 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child3\fR [\fB\-\-child3\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBchild1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child1 command
+.TP
+\fBchild2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child2 command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_not_recursive.roff b/clap_mangen/tests/snapshots/flatten_not_recursive.roff
new file mode 100644
index 00000000000..c72e34138bb
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_not_recursive.roff
@@ -0,0 +1,37 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child3\fR [\fB\-\-child3\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBchild1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child1 command
+.TP
+\fBchild2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child2 command
+.TP
+\fBchild3\fR [\fB\-\-child3\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child3 command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_recursive.roff b/clap_mangen/tests/snapshots/flatten_recursive.roff
new file mode 100644
index 00000000000..21ef1ab791f
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_recursive.roff
@@ -0,0 +1,34 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child3\fR [\fB\-\-child3\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBchild1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child1 command
+.TP
+\fBchild2\fR [\fB\-\-child2\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+child2 command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_single_hidden_command.roff b/clap_mangen/tests/snapshots/flatten_single_hidden_command.roff
new file mode 100644
index 00000000000..aef2e4c39c3
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_single_hidden_command.roff
@@ -0,0 +1,24 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent child1\fR [\fB\-\-child1\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_with_args_conflicts_with_subcommands.roff b/clap_mangen/tests/snapshots/flatten_with_args_conflicts_with_subcommands.roff
new file mode 100644
index 00000000000..be64adbdd50
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_with_args_conflicts_with_subcommands.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_with_external_subcommand.roff b/clap_mangen/tests/snapshots/flatten_with_external_subcommand.roff
new file mode 100644
index 00000000000..be64adbdd50
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_with_external_subcommand.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_with_global.roff b/clap_mangen/tests/snapshots/flatten_with_global.roff
new file mode 100644
index 00000000000..e9e273518f2
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_with_global.roff
@@ -0,0 +1,27 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_with_subcommand_required.roff b/clap_mangen/tests/snapshots/flatten_with_subcommand_required.roff
new file mode 100644
index 00000000000..c6802089606
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_with_subcommand_required.roff
@@ -0,0 +1,25 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent test\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.br
+\fBparent help\fR 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.SH SUBCOMMANDS
+.TP
+\fBtest\fR [\fB\-\-child\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+test command
+.TP
+\fBhelp\fR 
+Print this message or the help of the given subcommand(s)
diff --git a/clap_mangen/tests/snapshots/flatten_without_subcommands.roff b/clap_mangen/tests/snapshots/flatten_without_subcommands.roff
new file mode 100644
index 00000000000..d2855bfb428
--- /dev/null
+++ b/clap_mangen/tests/snapshots/flatten_without_subcommands.roff
@@ -0,0 +1,16 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH parent 1  "parent " 
+.SH NAME
+parent \- parent command
+.SH SYNOPSIS
+\fBparent\fR [\fB\-\-parent\fR] [\fB\-h\fR|\fB\-\-help\fR] 
+.SH DESCRIPTION
+parent command
+.SH OPTIONS
+.TP
+\fB\-\-parent\fR
+
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
diff --git a/clap_mangen/tests/testsuite/roff.rs b/clap_mangen/tests/testsuite/roff.rs
index 7831968047c..d7e65fe5943 100644
--- a/clap_mangen/tests/testsuite/roff.rs
+++ b/clap_mangen/tests/testsuite/roff.rs
@@ -1,4 +1,5 @@
 use crate::common;
+use clap::{Arg, Command};
 
 #[test]
 fn basic() {
@@ -141,3 +142,323 @@ fn flatten_help_true_subcommand_args_conflicts_with_subcommands() {
         .args_conflicts_with_subcommands(false);
     common::assert_matches(snapbox::file!["../snapshots/flatten_help.roff"], cmd);
 }
+
+#[test]
+fn flatten_basic() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child")),
+        );
+
+    common::assert_matches(snapbox::file!["../snapshots/flatten_basic.roff"], cmd);
+}
+
+#[test]
+fn flatten_help_cmd() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(
+            Arg::new("parent")
+                .long("parent")
+                .help("foo")
+                .long_help("bar"),
+        )
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .long_about("long some")
+                .arg(Arg::new("child").long("child").help("foo").long_help("bar")),
+        );
+
+    common::assert_matches(snapbox::file!["../snapshots/flatten_help_cmd.roff"], cmd);
+}
+
+#[test]
+fn flatten_with_global() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent").global(true))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child")),
+        );
+
+    common::assert_matches(snapbox::file!["../snapshots/flatten_with_global.roff"], cmd);
+}
+
+#[test]
+fn flatten_arg_required() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent").required(true))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child").required(true)),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_arg_required.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_with_external_subcommand() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .allow_external_subcommands(true)
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_with_external_subcommand.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_without_subcommands() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"));
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_without_subcommands.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_with_subcommand_required() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .subcommand_required(true)
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_with_subcommand_required.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_with_args_conflicts_with_subcommands() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .subcommand_required(true)
+        .args_conflicts_with_subcommands(true)
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("test")
+                .about("test command")
+                .arg(Arg::new("child").long("child")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_with_args_conflicts_with_subcommands.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_single_hidden_command() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("child1")
+                .hide(true)
+                .about("child1 command")
+                .arg(Arg::new("child").long("child1")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_single_hidden_command.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_hidden_command() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("child1")
+                .about("child1 command")
+                .arg(Arg::new("child").long("child1")),
+        )
+        .subcommand(
+            Command::new("child2")
+                .about("child2 command")
+                .arg(Arg::new("child").long("child2")),
+        )
+        .subcommand(
+            Command::new("child3")
+                .hide(true)
+                .about("child3 command")
+                .arg(Arg::new("child").long("child3")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_hidden_command.roff"],
+        cmd,
+    );
+}
+
+#[test]
+fn flatten_recursive() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("child1")
+                .flatten_help(true)
+                .about("child1 command")
+                .arg(Arg::new("child").long("child1"))
+                .subcommand(
+                    Command::new("grandchild1")
+                        .flatten_help(true)
+                        .about("grandchild1 command")
+                        .arg(Arg::new("grandchild").long("grandchild1"))
+                        .subcommand(
+                            Command::new("greatgrandchild1")
+                                .about("greatgrandchild1 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild1")),
+                        )
+                        .subcommand(
+                            Command::new("greatgrandchild2")
+                                .about("greatgrandchild2 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild2")),
+                        )
+                        .subcommand(
+                            Command::new("greatgrandchild3")
+                                .about("greatgrandchild3 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild3")),
+                        ),
+                )
+                .subcommand(
+                    Command::new("grandchild2")
+                        .about("grandchild2 command")
+                        .arg(Arg::new("grandchild").long("grandchild2")),
+                )
+                .subcommand(
+                    Command::new("grandchild3")
+                        .about("grandchild3 command")
+                        .arg(Arg::new("grandchild").long("grandchild3")),
+                ),
+        )
+        .subcommand(
+            Command::new("child2")
+                .about("child2 command")
+                .arg(Arg::new("child").long("child2")),
+        )
+        .subcommand(
+            Command::new("child3")
+                .hide(true)
+                .about("child3 command")
+                .arg(Arg::new("child").long("child3"))
+                .subcommand(
+                    Command::new("grandchild1")
+                        .flatten_help(true)
+                        .about("grandchild1 command")
+                        .arg(Arg::new("grandchild").long("grandchild1"))
+                        .subcommand(
+                            Command::new("greatgrandchild1")
+                                .about("greatgrandchild1 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild1")),
+                        )
+                        .subcommand(
+                            Command::new("greatgrandchild2")
+                                .about("greatgrandchild2 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild2")),
+                        )
+                        .subcommand(
+                            Command::new("greatgrandchild3")
+                                .about("greatgrandchild3 command")
+                                .arg(Arg::new("greatgrandchild").long("greatgrandchild3")),
+                        ),
+                )
+                .subcommand(
+                    Command::new("grandchild2")
+                        .about("grandchild2 command")
+                        .arg(Arg::new("grandchild").long("grandchild2")),
+                )
+                .subcommand(
+                    Command::new("grandchild3")
+                        .about("grandchild3 command")
+                        .arg(Arg::new("grandchild").long("grandchild3")),
+                ),
+        );
+
+    common::assert_matches(snapbox::file!["../snapshots/flatten_recursive.roff"], cmd);
+}
+
+#[test]
+fn flatten_not_recursive() {
+    let cmd = Command::new("parent")
+        .flatten_help(true)
+        .about("parent command")
+        .arg(Arg::new("parent").long("parent"))
+        .subcommand(
+            Command::new("child1")
+                .about("child1 command")
+                .arg(Arg::new("child").long("child1"))
+                .subcommand(
+                    Command::new("grandchild1")
+                        .about("grandchild1 command")
+                        .arg(Arg::new("grandchild").long("grandchild1")),
+                )
+                .subcommand(
+                    Command::new("grandchild2")
+                        .about("grandchild2 command")
+                        .arg(Arg::new("grandchild").long("grandchild2")),
+                )
+                .subcommand(
+                    Command::new("grandchild3")
+                        .about("grandchild3 command")
+                        .arg(Arg::new("grandchild").long("grandchild3")),
+                ),
+        )
+        .subcommand(
+            Command::new("child2")
+                .about("child2 command")
+                .arg(Arg::new("child").long("child2")),
+        )
+        .subcommand(
+            Command::new("child3")
+                .about("child3 command")
+                .arg(Arg::new("child").long("child3")),
+        );
+
+    common::assert_matches(
+        snapbox::file!["../snapshots/flatten_not_recursive.roff"],
+        cmd,
+    );
+}